[PATCH RFC v3 2/6] drm/sprd: add Unisoc's drm kms master

[tang pengchuan]

On Sun, Feb 23, 2020 at 12:26 PM tang pengchuan <kevin3.tang at gmail.com>
wrote:

>
>
> On Sun, Feb 23, 2020 at 5:27 AM Sam Ravnborg <sam at ravnborg.org> wrote:
>
>> Hi Kevin/tang.
>>
>> Thanks for the quick and detailed feedback.
>> Your questions are addressed below.
>>
>>         Sam
>>
>>
>> > > > +static int sprd_drm_bind(struct device *dev)
>> > > > +{
>> > > > +     struct drm_device *drm;
>> > > > +     struct sprd_drm *sprd;
>> > > > +     int err;
>> > > > +
>> > > > +     drm = drm_dev_alloc(&sprd_drm_drv, dev);
>> > > > +     if (IS_ERR(drm))
>> > > > +             return PTR_ERR(drm);
>> > > You should embed drm_device in struct sprd_drm.
>> > > See example code in drm/drm_drv.c
>> > >
>> > > This is what modern drm drivers do.
>> > >
>> > > I *think* you can drop the component framework if you do this.
>> > >
>> > I have read it(drm/drm_drv.c) carefully, if drop the component
>> framework,
>> > the whole our drm driver maybe need to redesign, so i still want to keep
>> > current design.
>> OK, fine.
>>
>> > > > +     sprd_drm_mode_config_init(drm);
>> > > > +
>> > > > +     /* bind and init sub drivers */
>> > > > +     err = component_bind_all(drm->dev, drm);
>> > > > +     if (err) {
>> > > > +             DRM_ERROR("failed to bind all component.\n");
>> > > > +             goto err_dc_cleanup;
>> > > > +     }
>> > > When you have a drm_device - which you do here.
>> > > Then please use drm_err() and friends for error messages.
>> > > Please verify all uses of DRM_XXX
>> > >
>> >   modern drm drivers need drm_xxx to replace DRM_XXX?
>> Yes, use of DRM_XXX is deprecated - when you have a drm_device.
>>
>> > >
>> > > > +     /* with irq_enabled = true, we can use the vblank feature. */
>> > > > +     drm->irq_enabled = true;
>> > > I cannot see any irq being installed. This looks wrong.
>> > >
>> > Our display controller isr is been register on crtc driver(sprd_dpu.c),
>> not
>> > here.
>>
>> I think you just need to move this to next patch and then it is fine.
>>
> Here is the advice given by Thomas Zimmermann, similar to the advice you
> gave.
> I have given thomas feedback about my questions, maybe thomas didn't see
> my email, so there is no reply.
>
> But I've always been confused, because irq is initialized in drm driver
> for other guys, why not for me?
> Can you help to tell the reason in detail, looking forward to your answers.
>
But I've always been confused, because the irq is initialized in the
sub-device code, but the device state is set by drm_drv.
Everyone else seems to do like this. why can't for me?

Can you help to tell the reason in detail, looking forward to your answers.

BR

>
> Thomas's suggestion：
>
> -------------------------------------------------------------------------------------------
> This line indicates the problem's design. The irq is initialized in the
> sub-device code, but the device state is set here. Instead both should
> be set in the same place.
>
> > +
> > +     /* reset all the states of crtc/plane/encoder/connector */
> > +     drm_mode_config_reset(drm);
> > +
> > +     /* init kms poll for handling hpd */
> > +     drm_kms_helper_poll_init(drm);
>
> Most of this function's code should be moved into the sub-device bind
> function.
>
> Here, maybe do:
>
>  * allocate device structures
>  * call component_bind_all()
>  * on success, register device
>
> The sub-device function should then do
>
>  * init modesetting, crtc, planes, etc.
>  * do drm_mode_config_reset()
>  * init vblanking
>  * init the irq
>  * do drm_kms_helper_poll_init()
>
> roughtly in that order. It makes sense to call drm_vblank_init() after
> drm_mode_config_reset(), as vblanking uses some of the mode-config fields.
>
> ------------------------------------------------------------------------------------------------------
>
>>
>>         Sam
>>
>>
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